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Aratati ca 1+3+5+......+(2n-1)este patrat perfact oricare ar fi n apartine N


Răspuns :

S1 = 1+3+5+.......+(2n-1) 
S2 = 2+4+6+........+2n = 2(1+2+3+.....+n) = 2·n(n+1)/2 = n(n+1)
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S1+ S2 =1+2+3+......+2n = 2n(2n+1)/2 = n(2n+1)
S1 = n(2n+1) - n(n+1) = n(2n+1 - n - 1) = n² = p.p.